Thermal Desorption Tubes Versatile Air Sampling for a Wide Range of Applications • Sensitive—concentrated sample collection to ppb/ppt levels. • Versatile—variety of sorbents to collect wide range of VOCs. • Efficient—reusable, time-saving alternative to solvent desorption tubes.
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Thermal Desorption: A Versatile Technique for a Wide Range of VOC Applications What is Thermal Desorption? Thermal desorption (TD) is a highly sensitive alternative to conventional sample collection procedures for volatile and semivolatile compounds, such as solvent desorption tubes. It is more efficient than other extraction methods and allows the selective concentration of target analytes, making it ideal for trace-level analysis by gas chromatography (GC/MS) across a wide range of applications. Thermal desorption is the process of collection and desorption of analytes from solid sorbents using heat and a flow of inert gas, rather than solvent extraction. Analytes are then focused on a cold trap prior to entering the analytical column, resulting in higher responses and narrow, more symmetric peaks. This is accomplished by interfacing a thermal desorption unit with a GC/MS (Figure 1). TD is highly sensitive and can significantly lower detection limits, by as much as 103, as it allows water to be purged, further facilitating the selective concentration of the compounds of interest. Thermal desorption tubes can be sampled actively with a sampling pump, or passively with a diffusion cap, and are reusable. Applications Thermal desorption has many air monitoring applications in a wide variety of industries including industrial hygiene, environmental air monitoring, odor profiling in the food and flavor industry, defense and forensic applications, and material emissions testing. TD is also compatible with many sample matricies in addition to air including solids (powders, fibers, films and granules), resins, pastes, liquids, and emulsions (Figure 2). Common applications include: • Workplace exposure monitoring. • Indoor/outdoor air testing. • Soil, water, and biological volatiles. • Residual volatiles, solvents etc. • Odor profiling for flavor and fragrance testing. • Fire debris, chemical warfare agents. • Material emissions from numerous consumer products.
Figure 1 Thermal desorption from Markes International.
Thermal desorption works well for almost all volatile, and many semivolatile compounds, and concentrations from ppm to ppt can be analyzed reliably. TD can be used for any volatile organic compound that is easily analyzed by GC, provided the sample matrix is compatible with the high temperatures required. Generally, this technique is not suitable for less volatile compounds, or compounds that are either not compatible with standard gas chromatography, or that require special care during GC analysis (e.g., on-column injection). Almost all other volatile compounds respond well, and a variety of sorbents are available to maximize the range of VOCs collected. Specifications and method applications for Restek thermal desorption tubes can be found on page 3. Significant sensitivity and efficiency improvements can be realized through thermal desorption. It is a versatile technique, suitable to many GC applications that require trace-level analysis of volatile compounds. Compare thermal desorption tubes to canister sampling using the chart on page 4 to determine which technique is right for you.
Figure 2 Thermal desorption is compatible with a wide range of sampling strategies. On-line air/ gas sampling Direct desorption of materials Vapors sampled onto sorbent tubes Headspace-trap or thermal
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100-200µL injection of vapor into GC/MS
Thermal Desorption Unit (TDU) Tubes • Variety of sorbents to collect a wide range of VOCs. • Use glass tubes for maximum inertness in active sampling. • Choose stainless steel tubes for either active or passive sampling. No sampling pump necessary for passive sampling with diffusion caps! • Individually etched with unique serial number for convenient sample identification. • Available unconditioned or preconditioned and ready to sample. Tubes are reusable after thermal desorption. High-quality thermal desorption tubes by Markes International. These sorbent tubes are suitable for ppt to ppm concentrations of volatile organic compounds (VOCs) in ambient, indoor, and industrial hygiene environments. Available in both stainless steel and glass (for thermally labile VOCs), they fit Markes ULTRA-UNITY, PerkinElmer, and Shimadzu thermal desorbers. Packed tubes come with a report detailing the total mass of sorbent in the tube; conditioned tubes also include a blank chromatogram. Thermal Desorption Tube Sorbent Tenax TA Graphitized Carbon Tenax GR/Carbopack B Carbopack B/Carbosieve SIII Tenax TA/Graphitized Carbon/Carboxen 1000 Carbopack C/Carbopack B/Carbosieve SIII
Applications Vapor phase organics from C6/7 to C26 Vapor phase organics from C5/6 to C14 Vapor phase organics from n-C5/6 to n-C20 (EPA Methods TO-14A/TO-15/TO-17) Vapor phase organics from n-C2/3 to n-C12/14 (EPA Methods TO-14A/TO-15/TO-17) Vapor phase organics from C2/3 to C20 Vapor phase organics from n-C2/3 to n-C16/20 (EPA Methods TO-14A/TO-15/TO-17)
Thermal Desorption Unit Tubes, Unconditioned and Conditioned & Capped
Description TDU Tubes, Tenax TA TDU Tubes, Graphitized Carbon TDU Tubes, Tenax GR/Carbopack B TDU Tubes, Carbopack B/ Carbosieve SIII TDU Tubes, Tenax TA/ Graphitized Carbon/Carboxen 1000 TDU Tubes, Carbopack C/ Carbopack B/Carbosieve SIII
Unconditioned Stainless Steel Glass qty. cat.# price cat.# price 10-pk. 24056 24062 10-pk. 24057 24063 10-pk. 24058 24064
Conditioned & Capped Stainless Steel Glass cat.# price cat.# price 24080 24086 24081 24087 24082 24088
10-pk. 24059
24065
24083
24089
10-pk. 24060
24066
24084
24090
10-pk. 24061
24067
24085
24091
method applications Method US EPA ASTM NIOSH DIN EN ISO
Application TO-17 D-6196 2549 16017
Specifications Dimensions: 1/4" OD x 3-1/2" long Low sampling rates: 0.01-0.20 L/min. (<10L total volume) Long-term storage caps are supplied with conditioned tubes
24061
24062 24067
Thermal Desorption Unit Tubes, Empty Description TDU Tubes, Empty
qty. 10-pk.
Stainless Steel cat.# price 24054
cat.# 24055
Glass
Stainless Steel cat.# price 24075 qty. ea. 10-pk. 10-pk.
cat.# 24076 cat. 24077 24078 24079
price
24054
Thermal Desorption Unit Tubes, Calibration Description TDU Tubes, Calibration, Tenax TA 1cm Bed Description Calibration Solution Loading Rig Calibration Solution Loading Rig 9.5mm Replacement Septa Certified Reference Standard, 100ng BTX on Tenax TA
qty. 10-pk.
24055
Glass price price
24071
Thermal Desorption Unit Tubes, Accessories Description /4" Brass Cap and PTFE Ferrules 1 /4" PTFE Ferrules CapLok Tool Pen Clip TubeMate Tool 1 /4" Stainless Steel Union and PTFE Ferrules Diffusion Caps 1
Benefits/Uses Long-term storage of blank/sampled tubes. Long-term storage caps. Use for tightening long-term storage caps. Assists with tube packing. Use for connecting tubes in series. Required for diffusive sampling with stainless steel tubes.
qty. 20-pk. 20-pk. ea. 10-pk. ea. 10-pk. 10-pk.
cat. 24068 24069 24070 24071 24072 24073 24074
price
24070
24074
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Thermal Desorption Tubes vs. Canister Sampling Use the information below to determine which VOC sampling technique is best suited for your application. Similarities Between Thermal Desorption Tubes and Canisters • Reusable sampling device. • Long product lifetime. • Long-term sample stability. • Blank certification required prior to sampling. • Sample concentration required before GC/MS analysis. • Dry purge helpful to remove moisture before GC injection.
• Ppt sensitivity. • Method acceptance. • Collection of wide range of VOCs with single device. • Useful for screening of unknowns. • Leak tightness critical to maintaining sample integrity and preventing contamination of a clean device.
tech guides Thermal desorption application guides are available for a broad range of markets. Request your FREE copy today using these part numbers.
Differences Between Thermal Desorption Tubes and Canisters Thermal Desorption Tubes
Canisters
Methods
US EPA TO-17; ASTM D6196; ISO 16017; ISO 16000-6; NIOSH 2549
US EPA TO-14A, TO-15; ASTM D5466 OSHA PV2120; NIOSH Protocol Draft
World-wide acceptance
Gold standard for US ambient air market
Applications
Ambient air, indoor air, industrial hygiene Material emissions Food & flavor Chemical weapons
Ambient air, indoor air, vapor intrusion, emergency response
Environmental Air Monitoring and Occupational Health & Safety EVTG1034
C3 to C30
Handling
Light weight for personal monitoring and general ease of use
Larger and heavier; more costly to ship
Sampling
Active sampling with sampling pump or diffusive sampling without pump is possible with determined diffusion coefficients for each compound.
Passive sampling, no sampling pump required. Longterm sampling possible without battery to recharge.
Integrated sampling only
Grab & integrated sampling
Concentrated sample
Whole air
Proper sorbent selection recommended in methodology.
N/A
Must sample below sorbent breakthrough volumes to avoid sample loss and irreversible adsorption on sorbent
N/A
Large sample volumes >100L
Sample volume is function of canister size, 15L max
Tube dimensions are instrument specific
Compatible with all manufacturer sample concentrators
1 injection, more injections possible for some instrumentation
Multiple sample injections
Concentration range ppt to ppm
Ppt to ppm
Analysis
Residual Volatiles & Materials Emissions Testing GNTG1035
Some sorbents prone to artifact formation.
Low blanks when properly cleaned.
Storage
Sample storage at 4°C recommended for multi-bed tubes to prevent potential migration of compounds to more retentive sorbent which maybe difficult to recover.
Room temperature
Cleaning
Analytical process automatically cleans tube for reuse. Cleans as it analyzes. Conditioning/cleaning and analysis incorporated in one thermal desorption unit.
Canister cleaning requires separate equipment as additional step prior to background certification and sampling.
Cost
$50-130 each
$200-700 each
Defense & Forensic CFTG1036
Food, Flavor, Fragrance & Odor Profiling FFTG1037
Questions about this or any other Restek® product? Contact us or your local Restek® representative (www.restek.com/contact-us). Restek® patents and trademarks are the property of Restek Corporation. (See www.restek.com/Patents-Trademarks for full list.) Other trademarks in Restek® literature or on its website are the property of their respective owners. Restek® registered trademarks are registered in the U.S. and may also be registered in other countries.
© 2008 Restek Corporation. All rights reserved. Printed in the U.S.A.
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Lit. Cat.# EVFL1065
